The CONTECH® dovetail or U-frame twistlock B-45 is a bottom twistlock used in combination with a dovetail or U-frame FR-31B, FR-31Q (elongated) or a FR-32B/A. It has a guiding angle of 45 degrees to secure the corner castings of containers on board of a vessel. As the twistlock is placed on top of the hatch cover or deck structure all forces are transmitted through the twistlock.